Hydrodynamic fluid film journal bearing

ABSTRACT

The top foil (12) of the hydrodynamic fluid film journal bearing (10) carries opposing tabs (23,25) at the side edges adjacent the free end (17) thereof and extends radially outward to fit adjacent to the side edges (19,21) of the intermediate foil 14 and the ends of the key 18 when rolled into a cylinder and inserted into the bore of sleeve (24) to prevent skewing of the top foil. In another embodiment skewing is prevented by incorporating opposing tabs (37,39,50,52) at the free ends (31,54) of the top foil (12a) and intermediate foil (14a) that project through predetermined sized slots (40,42) formed in the side edges (44,46) at the fixed end of intermediate slot (14a). The tabs overlie the side edges of the intermediate foil (14b) and bump foil (15) when rolled into a cylinder and prevent skewing and enhancing journal bearing performance.

TECHNICAL FIELD

This invention relates to journal bearings and particularly toanti-skewing means for a hydrodynamic fluid film air bearing.

BACKGROUND ART

As is well known in the bearing technology, the hydrodynamic air bearingconsists of a top foil, an intermediate foil and bump foil that arereversed rolled into a cylindrical shape that, in turn, is mountedwithin a sleeve for radially supporting a rotating shaft. An example ofapparatus utilizing this type of bearing is the air cycle machinesutilized for cooling aircraft manufactured by the Hamilton Standarddivision of United Technologies Corporation, the assignee of this patentapplication. In these designs, one end of each foil is secured while theopposite end is free. Upon reaching a predetermined speed, the air inthe sleeve is forced between foils that form wedges or air pockets whichserve as a cushion for supporting the shaft without the need of liquidlubrication. It has been found that on occasion, the free end of thefoils would move axially and become skewed either during operation ofthe rotating machinery or when the journal air bearing is beinginstalled. The effect of the skewing is that the bearing tightens whichincreases shaft torque and under certain circumstances could preventproper air film formation resulting in malfunction of the bearing. Thisinvention serves to obviate this problem by providing means forpreventing the foils from skewing. In one embodiment this inventioncontemplates incorporating end tabs at the end of the free end of thetop foil that fit into the keyway and in another embodiment tabs at theside edges assure that the top foil in the first embodiment and all thefoils in the second embodiment remain in the cylindrical shape.

SUMMARY OF THE INVENTION

An object of this invention is to provide and improved hydrodynamicfluid film journal bearing.

A feature of this invention is to provide side tabs to the free end ofthe top foil of the journal bearing to hold it in a cylindrical shape.In another embodiment the tabs are mounted at opposite sides of the endof the free end of the top foil that extend so as to overlap the sideedges of the intermediate foil and bump foil to also hold all the foilsin the cylindrical shape.

The foregoing and other features of the present invention will becomemore apparent from the following description and accompanying drawings.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is an exploded view in perspective illustrating one embodiment ofthe invention incorporated in the hydrodynamic fluid film journalbearing which is shown in the uncoiled position and includes a phantomview in schematic showing the bearing in the coiled position;

FIG. 2 is a sectional view taken along the longitudinal axis of thehydrodynamic fluid film journal bearing of the embodiment of FIG. 1;

FIG. 3 is a partial sectional view taken along lines 3--3 of FIG. 2;

FIG. 4 exemplifying another embodiment of this invention and is a planview of the uncoiled hydrodynamic fluid film journal bearing;

FIG. 5 is a front view of the bearing depicted in FIG. 4;

FIG. 6 is an end view of the bearing in FIG. 5 when in the coiledposition; and

FIG. 7 is an enlarged partial view taken along lines 7--7 of FIG. 6illustrating the details of the invention.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT

One embodiment of this invention one of the preferred embodiments canbest be understood by referring to FIGS. 1-3 which show the hydrodynamicfluid film journal bearing generally illustrated by reference numeral 10comprising top foil 12, intermediate foil 14 and bump foil 15. The topfoil 12 and intermediate foil 14 which are made from sheet metal stockwith a given spring rate are attached end to end by any suitable bondingmeans such as welding, brazing or the like at the weldment juncture 16which is in alignment with the key 18. Key 18 which lies transverse tothe longitudinal axis of the foils extends in a radial direction whenthe foils are wrapped into a cylinder about the axis of rotation A asshown as reference numeral 20 in the phantom view. As will be describedin further detail hereinbelow, the key 18 fits into a transverse slot orkeyway 22 formed in the wall 23 on the inner diameter of sleeve 24. Thebump foil 15 which is formed from a corrugated thin sheet metal materialhaving a given spring rate is wrapped around the top foil 12 and theintermediate foil 14 when in the coiled position to form a cylinderadapted to fit into the bore of sleeve 24 adjacent to wall 23. As willbe appreciated from the foregoing, the top foil, intermediate foil 14and bump foil 15 are configured in the same rectangular shape and arewrapped around in a reverse roll to form a cylinder such that wheninserted into sleeve 24 the outer foil 12 surrounds the shaft (notshown), the bump foil 15 is adjacent to wall 23, and the key 18 extendsinto the keyway 22 of the sleeve 24. The inner face 28 of top foil 12which lies adjacent to the rotating shaft (not shown) is preferablycoated with a dry lubricant so that when the shaft is accelerating toits operating speed during start up or decelerating as the shaft iscoasting to stop, and when the pressure of the air in the wedge of thefoils is not sufficient to support rotation, the dry lubricant willserve as an anti-friction means for maintaining wear and operability ofthe bearing. When in the operating condition and the shaft has reached apredetermined speed the pressure of the air that is forced into thewedges formed between the over lying surfaces of the top foil 12,intermediate foil 14 and bump foil 15 serves to support the shaft andthe spring rates of the foils is selected to obtain the propercompliance of the bearing.

In accordance with this invention, the width of the free end 17 is madewider than the other portion of top foil 12 to extend beyond the sideedges 11 and 13. This extended portion is bent radially outwardlyadjacent to the stress relief slots 21 and 23 to define tabs 25 and 27.As seen in FIG. 3 which is taken along lines 3--3 of FIG. 2 when the topfoil and intermediate foil are wrapped as depicted by the arrows B andC, (FIG. 1) respectively to form a cylinder the tabs 25 and 27 extendinto keyway 22 and overlie a portion of the opposing side edges 15 and17 of the intermediate foil 14 and opposing ends of key 18. Thisobviously prevents the top foil 12, intermediate foil 14 and bump foil15 from moving axially and deforming the cylindrical shape and becomingskewed.

While this embodiment does not show all the details of the finalconfiguration of the hydrodynamic fluid film journal bearing, it isdisclosed herein to detail the inventive portion of this type of journalbearing and the details of the final design configuration, as oneskilled in this art will appreciate, will depend upon the particularapplication for the intended use. Obviously, other methods of formingthe tabs at the end of the top foil may be employed without departingfrom the scope of this invention.

Referring next to FIGS. 4-7 which depict another embodiment of thisinvention disclosing the hydrodynamic fluid film journal bearing thathas been fully designed for a particular application and includeselements common to the hydrodynamic fluid film journal bearing depictedin FIGS. 1-3, namely, the top foil 12a, the intermediate foil 14a andbump foil 15, modified to include another anti-skewing means. In thisdescription, all like elements in all the Figs. are depicted with thesame reference numerals.

In accordance with this invention and referring particularly to FIG. 4,the free end 31 of the top foil 12a is slit at 32 and 34 a shortdistance inwardly from the side edges 36 and 38 and are bent radiallyoutward (into the paper as shown in this FIG. 4) to form tabs 37 and 39that ultimately fit into keyway 22. It should be understood that forpurposes of this description this embodiment is intended for use withthe sleeve 24 depicted in FIG. 2. Because the intermediate foil 14 wrapsaround the top foil 12a, slots 40 and 42 adjacent to key 16 are cut ashort distance inwardly into the side edges 44 and 46 of intermediatefoil 14a to allow the tabs 37 and 39 to project into keyway 22. Tabs 50and 52 formed at opposite ends of the free end 54 of intermediate foil14a are slit and bent similar to tabs 37 and 39 to project outwardly asshown in FIG. 4. When reversed rolled, tabs 50 and 52 extend radiallyoutwardly to bear against one end 31 of bump foil 15 and tabs 37 and 39bear against the opposite end of bump foil 15.

As best seen in FIGS. 6 and 7 the foils are reversed rolled to form acylinder that fits into sleeve 24 and the key 18 similar to that shownin FIG. 3 fits into keyway 22. Obviously, since tabs 37 and 39 fit intothe diametrically opposite slots 40 and 42 and the width of the tabs anddepth of the slots are equally dimensioned, top foil 12a is constrainedaxially. This prevents the top foil from skewing such that the cylindercannot be deformed. Like the embodiment disclosed in FIGS. 1-3, thisembodiment prevents skewing so that there is no deficit in theperformance of these journal bearings and as a matter of fact theperformance are at the optimum. This prevents the foils from slidingaxially to distort the cylinder and skew the free ends which wouldincrease bearing shaft torque, tighten the bearings and prevent anoptimum air film form being developed, all of which would at the veryleast hinder performance, or cause a malfunction of the bearing.

For illustration of affixing the key to the top foil in both embodimentsand for the sake of simplicity and convenience FIG. 5 is used forexplanation purposes. As noted, the fixed end 58 of top foil 12 overliesthe key 16 and is bonded thereto in a known suitable manner as describedabove and the fixed end 60 is bent inwardly to form a shoulder tocomplement and bear against the side edge of key 16 so as to be likewisebonded thereto by suitable means.

Although this invention has been shown and described with respect todetailed embodiments thereof, it will be appreciated and understood bythose skilled in the art that various changes in form and detail thereofmay be made without departing from the spirit and scope of the claimedinvention.

We claim:
 1. For a hydrodynamic fluid film journal bearing having a topfoil, an intermediate foil and bump foil, the improvement comprising tabmeans on the top foil for preventing the top foil from moving axially todeform the cylindrical shape when the top foil, intermediate foil andbump foil are wrapped into a cylinder, said top foil includes anelongated flat rectangularly shaped member having opposing ends andopposing sides, a key attached to one of said opposing ends of saidrectangularly shaped member, said tab means includes opposing projectingportions at the other end of said opposing ends each extending beyondsaid opposing sides, said opposing projecting portions being bent tooverlie a portion of said opposing side edges of said top foil whenrolled into a cylinder to prevent said top foil from skewing.
 2. For ahydrodynamic fluid film journal bearing as claimed in claim 1 includingstress relief slots formed in said opposing side edges adjacent to eachof said projecting portions.
 3. For a hydrodynamic fluid film journalbearing as claimed in claim 1 wherein said intermediate foil includes asimilar shaped rectangular member having other opposing side edges andother opposing ends, one of said other opposing ends being attached tosaid key to form an larger elongated rectangular member to be rolled andoverlie the top foil to define a cylinder, said similar shaped elongatedmember including opposing side edges, said tab means overlying a portionof each of said opposing side edges of said intermediate foil to preventsaid top foil, said intermediate foil from skewing.
 4. For ahydrodynamic fluid film journal bearing as claimed in claim 3 whereinsaid bump foil includes another elongated corrugated member defining arectangular shaped member when rolled overlies said cylinder, saidelongated corrugated member including opposing side edges, said tabmeans overlying a portion of each of said opposing side edges of saidintermediate foil and opposing side edges of said bump foil to preventsaid top foil, said intermediate foil and said bump foil from skewing.